Degradation Rate Of Cellulose Research Articles

Evaluation of maifanite and silage as amendments for green waste composting

Composting is a popular method for recycling organic solid wastes including agricultural and forestry residues. However, traditional composting method is time consuming, generates foul smells, and produces an immature product. The effects of maifanite (MF; at 0%, 8.5%, and 13.5%) and/or silage (SG; at 0%, 25%, and 45%) as amendments on an innovative, two-stage method for composting green waste (GW) were investigated. The combined addition of MF and SG greatly improved composting conditions, reduced composting time, and enhanced compost quality in terms of composting temperature, bulk density, water-holding capacity, void ratio, pH, cation exchange capacity, ammonia nitrogen content, dissolved organic carbon content, crude fibre degradation, microbial numbers, enzyme activities, nutrient contents, and phytotoxicity. The two-stage composting of GW with 8.5% MF and 45% SG generated the highest quality and the most mature compost product and did so in only 21 days. With the optimized composting, the degradation rate of cellulose and hemicellulose reached 46.3 and 82.3%, respectively, and the germination index of Chinese cabbage and lucerne was 153 and 172%, respectively, which were all far higher than values obtained with the control. The combined effects of MF and SG on GW composting have not been previously explored, and this study therefore provided new and practical information. The comprehensive analyses of compost properties during and at the end of the process provided insight into underlying mechanisms. The optimized two-stage composting method may be a viable and sustainable alternative for GW management in that it converts the waste into a useful product.

Composting-vermicomposting of green waste processing spiked with cow dung.

To accelerate the resource utilization of green waste, this study considered the combination of composting disposed green waste mixed with cow dung by employing Eisenia fetida. After pre-composting green waste for 60 d, seven treatments were prepared for vermicomposting by mixing green waste (pre-composted materials) with cow dung at ratios (dry weight) of 0(T0, without earthworms as a control), 0(T1), 2%(T2), 4%(T3), 6%(T4), 8%(T5), and 10%(T6). Growth and reproductive performance of E. fetida in different treatments were measured after 60 d of vermicomposting with a plant cultivation experiment (Calathea veitchiana) being conducted to estimate the quality and maturity of the final vermicompost. A complete random design with treatments of T0, T1, T2, T3, T4, T5, T6 and 30 replications. At the end of cultivation, five plants were randomly selected from each treatment and were analyzed for the plant growth parameters. Results showed that final products of all treatments with earthworms (T1-T6) were significantly higher (P < 0.05) in nutritional element content and plant growth parameters than T0. Moreover, in comparison with pure green waste treatment (T1), treatments with the addition of cow dung significantly (P < 0.05) increased the rate of growth and reproduction of earthworms, significantly (P < 0.05) accelerated the degradation rate of cellulose and lignin, and significantly (P < 0.05) increased nutrient contents of the final vermicompost product. Moreover, with the addition of cow dung, significantly (P < 0.05) increaseed in microbial population (bacteria, fungi, and actinomycetes) in vermicomposts were recorded. Among treatments T2-T6, T5 and T6 had significantly (P < 0.05) higher fertilizer value for the final product as well as significantly (P < 0.05) higher growth and fecundity of E. fetida. Thus, the combination of both processes (composting + vermicomposting) could be suitable for disposing cow dung and green waste with the green waste mixed with cow dung treatments at rates of 8% (T5) and 10% (T6) improving the efficiency and quality of the vermicompost.

Methods for determining the methane generation potential and methane generation rate constant for the FOD model: a review.

In the first order decay (FOD) model of landfill methane generation, the methane generation potential ( L0) and methane generation rate constant ( k) for both bulk municipal solid waste (MSW) and individual waste components have been determined by a variety of approaches throughout various literature. Differences in the determination methods for L0 and k are related to differences in our understanding of the waste decomposition dynamics. A thorough understanding of the various available methods for determining L0 and k values is critical for comparative study and the drawing of valid conclusions. The aim of this paper is to review the literature on the available determining methods and the ranges for L0 and k values of both bulk MSW and individual waste components, while focusing on understanding the decomposition of waste, including the role of lignin. L0 estimates in the literature are highly variable and have been derived from theoretical stoichiometric calculations, laboratory experiments, or actual field measurements. The lignin concentration in waste is correlated with the fraction of total degradable organic carbon (DOCf) that will actually anaerobically degrade in the landfill. The k value has been determined by precipitation rates, laboratory simulations, aged-defined waste sample, and model fitting or regression analysis using actual gas data. However, the lignin concentration does not correlate well with the k value, presumably due to the impact of lignin arrangement and structure on cellulose bioavailability and degradation rate. In sum, this review summarizes the literature on the measurement of L0 and k values, including the dynamics and decomposition of bulk MSW and individual waste components within landfills.

The Effect of Digested Manure on Biogas Productivity and Microstructure Evolution of Corn Stalks in Anaerobic Cofermentation.

The anaerobic fermentation of crop straw and animal wastes is increasingly used for the biogas and green energy generation, as well as reduction of the environmental pollution. The anaerobic cofermentation of corn stalks inoculated by cow dung was found to achieve higher biogas production and cellulose biodegradation. In this study, the effect of mixing corn stalks with cow dung at five different fermentation stages (0, 7, 15, 23, and 31 days of the total fermentation cycle of 60 days) on the further cofermentation process was explored, in order to optimize the corn straw utilization rate and biogas production capacity. In addition, the straw microstructure evolution was investigated by the SEM and XRD methods to identify the optimal conditions for the straw biodegradation process enhancement. The five test groups exhibited nearly identical total biogas productivity values but strongly differed by daily biogas yields (the maximal biogas generation rate being 524.3 ml/d). Based on the degradation characteristics of total solids (TS), volatile solids (VS), and lignocellulose, groups #1 and #3 (0 and 15 days) had the most significant degradation rates of VS (43.73%) and TS (42.07%), respectively, while the largest degradation rates of cellulose (62.70%) and hemicellulose (50.49%) were observed in group #4 (23 days) and group #1 (0 days), respectively. The SEM analysis revealed strong microstructural changes in corn stalks after fermentation manifested by multiple cracks and striations, while the XRD results proved the decrease in peak intensity of cellulose 〈002〉 crystal surface and the reduced crystallinity after cofermentation. The results of this study are assumed to be quite instrumental to the further optimization of the corn stalk anaerobic digestion by inoculation with digested manure for lignocellulose degradation enhancement and biogas productivity improvement.

KINETIC AND ENZYME RECYCLING STUDIES OF IMMOBILIZED b-GLUCOSIDASE FOR LIGNOCELLULOSIC BIOMASS HYDROLYSIS

b-glucosidases are very important in the improvement of cellulose degradation rates by diminishing the inhibition of end products. Although, cellulase cost has reduced significantly in last decade but still the high costs of biomass saccharification is one of the main challenges for the commercialization of ethanol from LC biomass. In this work, -glucosidase immobilization in calcium alginate was optimized using response surface methodology. 89% immobilization efficiency was achieved under optimum conditions (i.e., calcium alginate 4.19% (w/v), calcium chloride 0.14 M and -glucosidase 4.42% (v/v) or 57.46 U/mL of reaction mixture). pH and temperature optima of both free and immobilized -glucosidase was found to be 5 and 50 C, respectively. Enzyme kinetics of free and immobilized -glucosidase was done to evaluate Michaelis constant (Km) and Vmax values, using pnitrophenyl- -D-glucopyranoside (pNPG) as the substrate and glucose as inhibitor. Increase in Km value (0.995 mM) for immobilized -glucosidase as compared to the free -glucosidase (0.617 mM) was observed. A decrease in Vmax from (1191.74 mol min-1 for free -glucosidase) to (736.65 mol min-1 immobilized -glucosidase) was observed after immobilization. Glucose was found to inhibit -glucosidase by competitive mode of inhibition (Ki= 3.01 mM). Studies were carried out in a batch reactor using 2% cellobiose, 0.1 M sodium acetate buffer, 5 pH and 50 C. 84% cellobiose to glucose conversion was found in first cycle which was about 67% in fifth cycle. This study suggests that enzyme immobilization improved enzyme stability, substrate inhibition and permits enzyme reusability.

Decomposition of asparagus old stalks by Pleurotus spp. under mushroom-growing conditions

Abstract The aim of this work is to evaluate the decomposition of asparagus old stalks by five species of Pleurotus under mushroom-growing conditions. P. ostreatus gave the highest yield (270 g/bag) of fruit bodies at the first flush and the highest lignin degradation rate (68.4%) and cellulose degradation rate (56.2%) of asparagus old stalks substrate, followed by P. geesteranus, P. abalonus, P. eryngii and P. nebrodensi; P. geesteranus gave the highest hemicellulose degradation rate (35.8%). By contrast, the five species of Pleurotus had stronger decomposition ability to lignin and cellulose and weaker decomposition ability to hemicellulose in asparagus old stalks substrate. All the species reached their maximal carboxymethyl cellulose, xylanase, laccase, manganese dependent peroxidase and filter paper activities at the primordial stage. Moreover, the activity peaks of these lignocellulolytic enzymes of P. ostreatus were higher than that of other four species.

Anaerobic digestion of spent mushroom substrate under thermophilic conditions: performance and microbial community analysis.

Spent mushroom substrate (SMS) is the residue of edible mushroom production occurring in huge amounts. The SMS residue can be digested for biogas production in the mesophilic anaerobic digestion. In the present study, performance of batch thermophilic anaerobic digestion (TAD) of SMS was investigated as well as the interconnected microbial population structure changes. The analyzed batch TAD process lasted for 12days with the cumulative methane yields of 177.69mL/g volatile solid (VS). Hydrolytic activities of soluble sugar, crude protein, and crude fat in SMS were conducted mainly in the initial phase, accompanied by the excessive accumulation of volatile fatty acids and low methane yield. Biogas production increased dramatically from days 4 to 6. The degradation rates of cellulose and hemicellulose were 47.53 and 55.08%, respectively. The high-throughput sequencing of 16S rRNA gene amplicons revealed that Proteobacteria (56.7%-62.8%) was the dominant phylum in different fermentative stages, which was highly specific compared with other anaerobic processes of lignocellulosic materials reported in the literature. Crenarchaeota was abundant in the archaea. The most dominant genera of archaea were retrieved as Methanothermobacter and Methanobacterium, but the latter decreased sharply with time. This study shows that TAD is a feasible method to handle the waste SMS.

Construction of a High Efficiency Anaerobic Digestion System for Vinegar Residue

The model of high solid anaerobic digestion was used by improving the degree of homogeneity of the reaction system and biogas slurry reflux to gradually increase the material load. The vinegar residue-efficient anaerobic digestion system was successfully constructed without pretreatment.The optimum anaerobic digestibility was observed when the material loading of the reaction system reached 6.15 g·(L·d)-1, when the amount of biogas produced per unit of dry material was 396 mL·g-1, and the amount of methane produced per unit of dry material was 211 mL·g-1. The degradation rate of hemicellulose reached 63.66%, which was the main reason for the improvement of anaerobic digestion performance. The degradation rates of cellulose and lignin were 21.46% and 24.43%, respectively. The lower degradation efficiency was mainly due to the complicated degradation of the benzene ring structure in lignin and hindered hydrolysis of cellulose, which had a shielding effect on cellulose degradation.

Cellulose–silk fibroin hydrogels prepared in a lithium bromide aqueous solution

Here, we present a new process for the preparation of cellulose–silk fibroin hydrogels using a concentrated lithium bromide (LiBr) aqueous solution. After mixing, the solutions of cellulose and silk fibroin that had each been dissolved separately in aqueous LiBr, the cellulose forms a gel as the solution cools to approximately 70°C, and silk fibroin is regenerated via treatment in methanol. Three grades of cellulose–silk fibroin hydrogels are prepared by controlling the amounts of cellulose and silk fibroin. The gels have highly porous, three-dimensional networks composed of long, interconnected fibrils. Through X-ray diffraction and ATR-FTIR analysis we show that the dissolution-regeneration of cellulose and silk fibroin induces a structural change in the crystal structure of cellulose II and silk II. While the porosity and swelling ratio of cellulose–silk fibroin gels is significantly reduced with the increased silk fibroin content, all the gels show high water uptake. The enzymatic degradation rates of cellulose–silk fibroin gels obviously reflect differences in the silk fibroin content, and cell adhesion and growth on cellulose–silk fibroin gels is enhanced with increased silk fibroin content. These cellulose–silk fibroin gels could provide novel properties that would be useful for biomaterial matrix applications.

The distribution of active β-glucosidase-producing microbial communities in composting.

The composting ecosystem is a suitable source for the discovery of novel microorganisms and secondary metabolites. Cellulose degradation is an important part of the global carbon cycle, and β-glucosidases complete the final step of cellulose hydrolysis by converting cellobiose to glucose. This work analyzes the succession of β-glucosidase-producing microbial communities that persist throughout cattle manure - rice straw composting, and evaluates their metabolic activities and community advantage during the various phases of composting. Fungal and bacterial β-glucosidase genes belonging to glycoside hydrolase families 1 and 3 (GH1 and GH3) amplified from DNA were classified and gene abundance levels were analyzed. The major reservoirs of β-glucosidase genes were the fungal phylum Ascomycota and the bacterial phyla Firmicutes, Actinobacteria, Proteobacteria, and Deinococcus-Thermus. This indicates that a diverse microbial community utilizes cellobiose. The succession of dominant bacteria was also detected during composting. Firmicutes was the dominant bacteria in the thermophilic phase of composting; there was a shift to Actinomycetes in the maturing stage. Proteobacteria accounted for the highest proportions during the heating and thermophilic phases of composting. By contrast, the fungal phylum Ascomycota was a minor microbial community constituent in thermophilic phase of composting. Combined with the analysis of the temperature, cellulose degradation rate and the carboxymethyl cellulase and β-glucosidase activities showed that the bacterial GH1 family β-glucosidase genes make greater contribution in cellulose degradation at the later thermophilic stage of composting. In summary, even GH1 bacteria families β-glucosidase genes showing low abundance in DNA may be functionally important in the later thermophilic phase of composting. The results indicate that a complex community of bacteria and fungi expresses β-glucosidases in compost. Several β-glucosidase-producing bacteria and fungi identified in this study may represent potential indicators of composting in cellulose degradation.

Lignocellulose biodegradation in the biodrying process of sewage sludge and sawdust

ABSTRACTLignocellulose degradation is important when applying biodrying treatment to sewage sludge intended for land use. This study investigated the lignocellulose degradation in the biodrying of sewage sludge and sawdust. The experiment analyzed lignocellulose content, lignocellulase activity, humic substances, and fungal communities. After biodrying, lignin, cellulose, and hemicellulose degradation rates were 48.4, 38.8, and 45.0%, respectively. Carboxymethyl cellulase, lignin peroxidase, and xylanase played key roles. During the thermophilic phase, more than 80% of the microorganisms in the sample contributing to lignocellulose degradation were Ascomycota. The lignocellulose degradation and a rate of increase in humic acid/fulvic acid of 380% benefit land use of biodrying product.

Effect of physicochemical pretreatments and enzymatic hydrolysis on corn straw degradation and reducing sugar yield

Straw lignocelluloses were converted to reducing sugar for possible use for bioenergy production via physicochemical pretreatments and enzymatic hydrolysis. The experiment was divided into 2 steps. The first step focused on breaking the crystal structure and removing lignin in corn straw. The lignin, hemicellulose, and cellulose degradation rates observed were 92.2%, 73.7%, and 4.6%, respectively, after corn straw was treated with sodium hydroxide (3% w/w) plus high-pressure steam (autoclave), 74.8%, 72.5%, and 4.3% after corn straw was treated with sodium hydroxide (8%, w/w) plus wet steam explosion, compared with native corn straw (P &lt; 0.05). The second step was enzymatic hydrolysis for the pretreated straw. The enzymatic hydrolysis could yield 576 mg/g reducing sugar and significantly degrade cellulose and hemicellulose contents by 93.3% and 94.4% for the corn straw pretreated with sodium hydroxide plus high-pressure steam. For the corn straw pretreated with sodium hydroxide plus wet steam explosion, the enzymatic hydrolysis could yield 508 mg/g reducing sugar, and degrade cellulose and hemicellulose contents by 83.5% and 84.2%, respectively, compared with the untreated corn straw (P&lt;0.05). Scanning electron microscopy showed that the physicochemical pretreatments plus enzymatic hydrolysis degraded corn straw to many small molecules. Thus, physicochemical pretreatments plus enzymatic hydrolysis converted lignocellulose to reducing sugar effectively.

Fungal community and cellulose-degrading genes in the composting process of Chinese medicinal herbal residues

The fungal community and the population of 16S rRNA, 18S rRNA and cellulose-degrading genes during the 30-day composting process of Chinese medicinal herbal residues were investigated using Illumina MiSeq and quantitative real-time PCR. An obvious succession of fungal communities occurred during the composting process. Unidentified fungi predominated in the raw materials. As composting progressed, Ascomycota became the most dominant phylum, with Aspergillus being the most dominant genus, and Aspergillus fumigatus making up 99.65% of that genus. Because of the inoculation of cellulolytic fungi in the mature stage, the cellulose degradation rate in inoculation groups was faster and the relative abundances of Aspergillus and the glycoside hydrolase family 7 genes were significantly higher than those in the control groups. These indicated that the fungal inoculants facilitated the degradation of cellulose, increased cellulolytic fungi and optimized the community structure.

Degradation of beech wood and wheat straw by Trametes gibbosa

The aim of this study was to optimize cultivation conditions for Mn-oxidizing peroxidases and laccase production and selective degradation of beech wood and wheat straw lignin by Trametes gibbosa. To promote lignin degradation, the effect of different carbon and nitrogen sources, type of cultivation, enzyme dynamics and inducers were studied. Solid-state cultivation was optimal for lignin degradation. Wheat straw was the optimal carbon source for peroxidase activities stimulating the synthesis of numerous isoforms. The dynamics of enzymatic activities showed that 19-day-old fermentation is optimal and that activities were directly associated with enzyme production. Alteration of nitrogen sources and inducers was applied to increase the rate of lignin degradation and decrease cellulose degradation. The presence of nitrogen in the form of (NH4)2SO4 and concentration of 10 mM significantly increased the extent and selectivity of delignification of wheat straw compared with cellulose (44.1 vs. 36.1%). The most effective and selective wheat straw degradation (52.0% of lignin vs. 31.3% of cellulose) was achieved by enriching the optimum medium, as defined above, with 1.0 mM p-anisidine. The optimum conditions for wheat straw processing to achieve delignification and production of highly active ligninolytic enzymes by T. gibbosa were (NH4)2SO4/wheat bran medium supplemented with p-anisidine. This study indicated the significant potential of optimizing external factors as a promising tool for induction and selectivity in the degradation of lignocelluloses by T. gibbosa as a pretreatment for several biotechnological processes.

Effects of Organic Loading Rate on Startup Performance of Anaerobic Digestion with Vinegar Residues

Biochemical methane potential experiments were conducted to investigate the effects of organic loading rate on the performance of anaerobic digesters with vinegar residues. According to the comparisons of methane production and liquid phase compositions, as well as thermogravimetry, X-ray Diffraction and infrared spectroscopy analyses, the conclusions could be drawn that:①Lower organic loading rate was better to mitigate the accumulation of VFAs and pH decrease during the hydrolysis and acidification of organic matters, which consequently improved methane production. When the inoculum to substrate ratio was 1:1[organic loading rate of 1.78 g·(L·d)-1, pH=7.60], the cumulative methane production was the highest, reaching 2249.7 mL, and the performance of the digesters was stable. The VFAs content increased with the increase of the organic loading rate, leading to the suppression and further the stop of methane production. And when the inoculum to substrate ratio was 1:4[organic loading rate of 7.12 g·(L·d)-1, pH=5.52], the simultaneous generation of acetate and lactic acids could be achieved at 8000 mg·L-1 and 2650 mg·L-1, respectively. ② As vinegar residues were short-range ordered with microcrystalline structure or mainly contained amorphous substances, they were more biodegradable than feedstocks such as corn stalk. During the anaerobic digestion processes, the degradation rates of lignin, cellulose and hemicellulose increased with the decrease of organic loading rate.

Pretreatment of lignocellulosic biomass by cattle rumen fluid for methane production: Bacterial flora and enzyme activity analysis

We attempted to develop a pretreatment method for methane fermentation of lignocellulosic biomass using cattle rumen fluid, treated as slaughterhouse waste. When rapeseed (Brassica napus L.) was added to the methane fermentation after being solubilized with rumen fluid, 1.5 times more methane was produced compared with untreated rapeseed. Analysis of the bacterial flora during rumen fluid treatment using the MiSeq next-generation sequencer showed that the predominant phylum shifted from Bacteroidetes, composed of amylolytic Prevotella spp., to Firmicutes, composed of cellulolytic and xylanolytic Ruminococcus spp., in only 6h. In total, 7 cellulolytic, 25 cello-oligosaccharolytic, and 11 xylanolytic bacteria were detected after investigating the most abundant sequences of detected taxa. The relative abundance of two Ruminococcus species (Ruminococcus albus and R. flavefaciens), known as cellulolytic, cello-oligosaccharolytic, and xylanolytic bacteria, increased with increasing cellulose and hemicellulose degradation rates, and, finally, comprised 48% of all operational taxonomic units. The chronological observation of enzyme activities showed that cellulolytic and xylanolytic activities increased 6h later, and that oligosaccharolytic activity increased 24h later. This study detected six bacteria that participate in the degradation of aromatics derived from lignin, which have rarely been reported in rumen fluid. The constitution of the detected bacteria suggests that the aromatics were converted into acetate via benzoate. The list of microbes that cover all lignocellulose-degrading candidates will provide fundamental knowledge for future studies focusing on rumen microbes.

Influence of humic acid supplemented to sheep diets on rumen enzymatic activity

The objective of the present study was to investigate how different levels of natural humic acid in the diet affect the hydrolases activity in the rumen of sheep. The experiment was carried out on three rumen-fistulated adult sheep. The control animals were fed a diet (K) containing 59.7% meadow hay, 28.4% crushed barley, 9.8% soybean oil meal and 2.1% vitamin mineral mixture. The experimental diets were composed of the control ration supplemented with humic acid (HUMAC natur AFM® containing 65% humic acid in dry matter) and supplied at doses of 10 g · d–1 (diet H10) or 20 g · d–1 (diet H20). Samples of rumen digesta were collected just before the morning feeding, as well as 2, 4, and 8 h afterwards. In the present study, the cellulolytic activity in the rumen digesta was higher (P &lt; 0.01) in sheep fed the K diet than it was in animals fed the H20 ration 2 h after feeding. However, the effect of humic acid on the cellulose degradation rate depended on the content of humic acid in the diet. The cellulolytic activity was increased 2 h after feeding in sheep fed the H10 diet as compared with animals fed the H20 ration (P &lt; 0.05). Sampling time had significant influence on the hydrolases activity in the rumen of sheep. In sheep fed the H10 ration, the cellulolytic activity was higher 8 h after feeding than it was before feeding and 4 h after feeding (P &lt; 0.05). In the H10 and H20 groups, the xylnalolytic activity was higher before feeding, but lower than it was in the control group K. The degradation rates of xylan were decreased 2 and 4 h after feeding in sheep fed the H10 and H20 rations and then increased 8 h after feeding (P &lt; 0.05). In sheep fed the H20 diet, the amylolitic activity 8 h after feeding was higher than it was 2 h after feeding (P &lt; 0.05). The effect of humic acid on the hydrolases activity in the rumen of sheep is not uniform and depends on the quantity of humic acid in the diet and on sampling time. Humic acid present in commercial HUMAC natur AFM® product enhances the initial rate of cellulose degradation in the rumen at a dose of 10 g · d-1. Thus, it may suggest that humic acid stimulates the growth of fibrolytic microorganisms in the rumen. On the other hand, the present results suggest that humic acid may reduce the rate of carbohydrate degradation in the rumen, since a higher hydrolases activity was observed before morning feeding and 8 h afterwards....

Comparative Analysis of Single-stage and Two-stage Fermentation Systems under Various Process Conditions

A comparative study of single-stage fermentation (wet or dry) and two-stage (wet-dry and dry-wet) fermentation systems was carried out under medium temperature conditions. The effect of the length of the first wet or dry fermentation stage (5-, 10-, 15-, 20-, and 25-d) in the two-stage anaerobic fermentation was investigated. The results showed that the gas production of wet fermentation and two-stage wet-dry fermentation was better than that of the dry fermentation and two-stage dry-wet fermentation. The cumulative gas production increased gradually with increased stage conversion times for the two-stage wet-dry fermentation. The gas production for the 20-d experimental group of the two-stage wet-dry fermentation system was the best. The cumulative biogas production in the anaerobic fermentation of straw correlated significantly with the changes in the degradation rates of volatile solids, cellulose, and hemicellulose (P < 0.01). The kinetic fitting analysis showed that the Reaction Curve (RC) model was more suitable for data modeling of the single-stage wet fermentation and two-stage wet-dry fermentation with straw than the Modified Gompertz (GM) and Modified Logistic (LM) models. The results of this study provided a theoretical basis for choosing a fermentation process for large-scale biogas production with straw.

Degradation of lignin and cellulose during foliar litter decomposition in an alpine forest river

AbstractLignin and cellulose are thought to be critical factors that affect the rate of litter decomposition; however, few data are available on their degradation dynamics during litter decomposition in lotic ecosystems, such as forest rivers, where litter can decompose much more rapidly than in terrestrial ecosystems. We studied the degradation of lignin and cellulose in the foliar litter of four dominant riparian species (willow:Salix paraplesia; azalea:Rhododendron lapponicum; cypress:Sabina saltuaria; and larch:Larix mastersiana) in an alpine forest river. Over an entire year's incubation, litter lignin and cellulose degraded by 14.7–100% and 57.7–100% of their initial masses, respectively, depending on litter species. Strong degradations of lignin and cellulose occurred in the prefreezing period (i.e., the first 41 d) during litter decomposition, and the degradation rate was the highest among all the decomposition periods regardless of litter species. Litter species, decomposition period, and environmental factors such as temperature and nutrient availability showed significant influences on lignin and cellulose degradation rates. Compared with previously reported data regarding the dynamics of lignin and cellulose during litter decomposition in terrestrial ecosystems, our results suggest that lignin and cellulose can be degraded much more rapidly in lotic ecosystems, indicating that the traditionally used two‐phased model for the dynamics of lignin in decomposing litter may not be suitable in lotic ecosystems.

Cellulose Dynamics during Foliar Litter Decomposition in an Alpine Forest Meta-Ecosystem

To investigate the dynamics and relative drivers of cellulose degradation during litter decomposition, a field experiment was conducted in three individual ecosystems (i.e., forest floor, stream, and riparian zone) of an alpine forest meta-ecosystem on the eastern Tibetan Plateau. Four litter species (i.e., willow: Salix paraplesia, azalea: Rhododendron lapponicum, cypress: Sabina saltuaria, and larch: Larix mastersiana) that had varying initial litter chemical traits were placed separately in litterbags and then incubated on the soil surface of forest floor plots or in the water of the stream and riparian zone plots. Litterbags were retrieved five times each year during the two-year experiment, with nine replicates each time for each treatment. The results suggested that foliar litter lost 32.2%–89.2% of the initial dry mass depending on litter species and ecosystem type after two-year’s incubation. The cellulose lost 60.1%–96.8% of the initial mass with degradation rate in the order of stream &gt; riparian zone &gt; forest floor. Substantial cellulose degradation occurred at the very beginning (i.e., in the first pre-freezing period) of litter decomposition. Litter initial concentrations of phosphorus (P) and lignin were found to be the dominant chemical traits controlling cellulose degradation regardless of ecosystems type. The local-scale environmental factors such as temperature, pH, and nutrient availability were important moderators of cellulose degradation rate. Although the effects of common litter chemical traits (e.g., P and lignin concentrations) on cellulose degradation across different individual ecosystems were identified, local-scale environmental factors such as temperature and nutrient availability were found to be of great importance for cellulose degradation. These results indicated that local-scale environmental factors should be considered apart from litter quality for generating a reliable predictive framework for the drivers of cellulose degradation and further on litter decomposition at a global scale.